1. Field of the Invention
The present invention relates to a radio frequency identification (RFID) tag, and more particularly, to a battery-assisted tag driven by an internal power source for improved recognition distance, and a wake-up method thereof.
This work was supported by the IT R&D program of MIC/IITA. [2005-S-106-02, Development of Sensor Tag and Sensor Node Technologies for RFID/USN]
2. Description of the Related Art
Generally, in a radio frequency identification (RFID) technique, tags are attached to respective objects, and unique identifications (IDs) of the objects are wirelessly recognized so that corresponding information can be collected, stored, processed, and traced in order to provide a service in association with the locations of the objects, remote processing, management, and information exchange between the objects. As a replacement of conventional barcodes, the technique is applied to various fields from material management and distribution to security. Therefore, it is expected to create a new market.
RFID systems are either battery-assisted or passive, according to how the tags are powered.
FIG. 1 is a functional block diagram of a conventional passive RFID tag.
When a signal of a continuous wave is received from an RFID reader through an antenna 110, a voltage booster 120 increases the voltage of the signal and supplies it to an electrically erasable programmable read-only memory (EEPROM) 130 and a controller 150 as a driving voltage.
A demodulator 140 demodulates a command of the RFID tag reader received through the antenna 110, and the controller 150 executes the command. Then, the result of executing the command is modulated by a modulator 160 and is transmitted through the antenna 110 to the RFID tag reader.
Accordingly, the passive tag is not assisted by a battery, but is driven using only the power of the continuous wave received through the antenna 110. Therefore, the recognition distance is limited to about 5 m, and recognition is unreliable when the tag is attached to a metal object.
Meanwhile, active and semi-active tags are battery-assisted, and thus have longer recognition distance than passive tags, but suffer from limited battery lifespan.